A close look at Indian rice grass
Native Americans used the staple for many foods for thousands of years, and it is now recognized as the state grass in Nevada and Utah
During June, at 6,000 feet on the Colorado Plateau, Indian rice grass was filling the meadows, waving its large, dark seeds in the wind. Indian rice grass, Achnatherum (or Oryzopsis or Stipa) hymenoides, is a drought-tolerant bunchgrass that grows from 1 to 2.5 feet tall.
In contrast to many other grass species, bunchgrasses do not have rhizomes that promote clonal growth and the formation of sod. Each individual bunchgrass grows as a clump, often with bare dirt between clumps.
Identification of Indian rice grass is relatively easy because its leaves are tightly rolled from the edges, forming narrow tubes. Its seeds develop in expanded panicles (branched columns of flowers), with long, undulating stalks or threads spread at distinctly wide angles, each bearing a single seed at its tip. These delicate and flexible forms move easily in the wind, giving the illusion of a fog of dark seeds.
Indian rice grass has a wide native geographic distribution, from British Columbia to Mexico and from the Pacific Ocean to its eastern margins in Minnesota, South Dakota, Nebraska, Kansas, Arkansas and Texas.
Top of the page: A field dominated by Indian rice grass on the Colorado Plateau. Above: The seeds of Indian rice grass develop at the ends of long stalks. Photos courtesy of Jeff Mitton.
This broad distribution is achieved by local adaptation to many habitats, including ponderosa pine forests, sagebrush, desert shrub, chaparral, piñon-juniper, prairie, plains grasslands and desert grasslands. When we also consider the latitudinal climate changes from Mexico to Minnesota, this is a remarkable range of habitats.
Studies of adaptation to a variety of environments reveal that seed dormancy varies both among and within habitats. Seed dormancy is the time that seeds lie in the soil without emerging in the spring and it is associated with both physical aspects of the seed and genetically controlled physiological characteristics of the embryo. Indian rice grass has both modes of seed dormancy.
A study of seed germination rates showed that less than 3% germinated after one year, but germination increased to 47% at six years and then dwindled to 1.5% in year 17. Variability in seed dormancy increases the probability that some seeds will be dormant during years of drought and fire, increasing the probability that some seeds will germinate in years with favorable conditions for germination, seedling establishment, growth and reproduction.
Seeds fall into three distinct size and shape categories: jumbo (big), globose (medium) and elongate (small, slender). A population may have seeds of one, two or three categories, which are determined by the thickness of the seed coat. The thicker the seed coat, the larger the seed and the longer the dormancy.
Because of the way Indian rice grass sets seed, a population is not a diverse collection of genotypes but is composed of separate, independent genetic lineages. That is, seed size and dormancy form genetic lineages with little evidence of genetic exchange among lineages.
Within seed size categories, genetic variation modifying embryo physiology and development drives a second mode of seed dormancy. So, Indian rice grass has both morphological and physiological modes to prevent all of the seeds from germinating in one year, clearly an adaptation to cope with the unpredictable weather conditions in western North America.
Indian rice grass was a diet staple for many groups of Native Americans, reaching far back in time. Considering only groups in the Four Corners area, Navajo and Apache turned the seeds into bread or, in combination with cornmeal, made porridge. Havasupai made a similar porridge, but also dried the seeds, ground them to flour and boiled the mixture to make dumplings. Hopi made rice grass tortillas. Paiute turned them into sauce and flour, while Zuni steamed the seeds and fashioned them into steamed grain balls.
A diverse group of wildlife species also consume the large, edible seeds of Indian rice grass, including buffalo, elk, deer, deer mice, voles, chipmunks, ground squirrels and all species of seed-eating birds.
Montina was a flour made from milled Indian rice seeds and marketed as a gluten-free flour by Amazing Grains. It was in development in the early 1990s and by 2003, more than 50 farms, most in Montana, were growing Indian rice grass for Amazing Grains. Unfortunately, its price was not competitive and it is no longer marketed.
To recognize the historic importance of Indian rice grass to the inhabitants of their state, Nevada and Utah adopted it as their state grass.
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